Printing unit wrapping strips of tobacco and a printing method

ABSTRACT

A printing unit for applying print marks to a wrapping strip in a cigarette rope machine of the tobacco processing industry is provided. The printing unit includes at least one printing cylinder, a counter-pressure cylinder in contact with the at least one printing cylinder, and a fastening device adapted to jointly attach and detach the at least one printing cylinder and the counter-pressure cylinder to the cigarette rope machine.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the priority of German patent document No. 101 30 225.8, filed Jun. 22, 2001, and is the National Stage of International Application No. PCT/EP02/06412, filed Jun. 12, 2002, the disclosures of which, as well as any patent and/or patent applications mentioned below, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to a printing unit for applying print marks to a wrapping strip in the tobacco-processing industry, in particular a cigarette paper strip in a cigarette-rope producing machine. The printing unit includes at least one printing cylinder that is in contact with a counter-pressure cylinder.

[0003] In continuously operating, rope producing machines for producing rod-shaped articles, such as cigarettes, cigars, cigarillos, filter rods or the like with the aid of an extruding process, print marks or print images are applied to wrapping paper strips in the tobacco industry, e.g. cigarette paper strips, such as the cigarette marks themselves or the name of the manufacturer or other information. The rope producing machines comprise correspondingly designed printing units, in which at least one driven printing cylinder is in contact with a counter-pressure cylinder with the material web to be imprinted being guided between these cylinders. At least during printing, the speeds of the printing cylinders and the continuously moving material webs are synchronized.

[0004] A printing unit for a double-rope machine is disclosed in British Patent Document 327 206, in which two print marks are applied onto a cigarette paper strip using one printing cylinder for each print mark. Both printing cylinders make contact with a counter-pressure cylinder, and the cigarette paper strip is guided between the printing cylinders and the counter-pressure cylinder.

BRIEF SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to permit a fast replacement of a printing unit of the above-mentioned type such that no involved assembly and adjustment operations with new printing cylinders are required, for example in case of a mark change. It is a further object to be able to adapt the lengths of printing sections quickly with a change in the cigarette length.

[0006] These and other objects are solved according to the present invention, which includes a fastening device which makes it possible to jointly fasten and detach premounted cylinders on the machine.

[0007] In one exemplary embodiment of the invention, the printing cylinder and the counter-pressure cylinder are positioned inside a bearing support that is detachably installed on the machine, such that they form a single unit with the support that can be attached or detached from the machine. The bearing support can include two bearing plates, between which the printing cylinder and, if necessary, the counter-pressure cylinder are arranged. The present invention makes it possible to remove the complete printing unit from the machine with essentially a single pulling operation and to install a new printing unit.

[0008] According to another exemplary embodiment the invention, the counter-pressure cylinder can be positioned so as to rotate freely on an spindle and an electric motor can be used to drive the printing cylinder. The fastening device can be mechanically connected to the bearing support and can be attached with one end to the machine. The fastening device can be provided with a bolt that supports the bearing support and is screwed at one end into the machine wall. The other end of the bolt can be provided with a lever for detaching or fastening the bearing support. The bolt can extend through bores in the bearing plates.

[0009] If a printing unit is removed from the machine as a result of a format change or mark change, following the installation of a new printing unit with premounted printing cylinder and counter-pressure cylinder on the machine, the printing cylinder must be positioned at a specific angle of rotation relative to the machine. According to a further embodiment of the invention, a position-specific coupling can be provided between the drive and the printing cylinder such that, following the installation of a new pre-mounted printing cylinder/counter-pressure cylinder unit, the printing cylinder assumes a predetermined angular position within the machine.

[0010] To obtain optimum printing qualities, the printing cylinder and the counter-pressure cylinder must be secured at a specific position relative to each other. In a further exemplary embodiment of the present invention, an adjustment device for minimal adjustments of the counter-pressure cylinder position relative to the printing cylinder. The adjustment device can include one or more screw bolts. An elastic, resilient bearing element, such as a rubber bushing, can aid the adjustment operation of the spindle.

[0011] The present invention is particularly suitable for a printing unit having two printing cylinders that make contact with one counter-pressure cylinder with a material web that is conveyed in between, and results in the particular advantage of allowing a pre-mounting, meaning the installation and adjustment do not occur at the machine.

[0012] If the print mark and/or the length of a printed section is changed, the printing unit can be adapted by simply exchanging it with another printing unit having new cylinders.

[0013] In a further exemplary embodiment of the present invention, an electric drive motor for the printing cylinder and a control unit emits control pulses for the drive motor, such that between printing operations, the rotational speed of the printing cylinder deviates from the printing speed during the printing operation. With the present invention, the lengths of the printed-on sections on the continuously moving material webs can be changed quickly and easily without requiring a gear transmission. In a further exemplary embodiment of the printing unit of the present invention, the printing unit does not operate at a uniform speed and is characterized by a stepping motor for driving the printing cylinder and a control unit for emitting control pulses for the stepping motor in which the control pulses are supplied with constant frequency to the stepping motor during a printing operation such that the printing elements on the printing cylinder move at the same speed as the material web, and are supplied with deviating frequency between two printing operations to move with deviating movements.

[0014] The control unit can be provided with an adjustment unit for changing the deviating frequency of the control pulses between two printing operations. The control unit can include a memory for storing the predetermined course of the frequency. The frequency can be changed according to a characteristic curve.

[0015] A separating wall can be provided in the space between the mechanisms supplying printing fluids to the individual printing cylinders. This wall prevents speckles of printing color that is supplied to one printing cylinder from reaching the other printing cylinder.

[0016] The present invention is not only suitable for use with a single-rope cigarette machine, but also with double-rope cigarette machines, in which two tobacco ropes are formed and processed into cigarettes. With the present invention, only a few manual operations are required for changing the printing unit in case of a mark change where a new print mark with a new print image is to be applied to the cigarette paper strip. These manual operations involve loosening a bolt with the aid of a lever, removing a bearing support and replacing it with another, pre-mounted bearing support, which is simply fitted on and secured with the aid of a corresponding bolt. The exact positioning is achieved with position-specific couplings. Following the removal of the printing unit, the printing cylinders and, if applicable, also the counter-pressure cylinder can be replaced and adjusted outside of the machines that continue to operate with the new printing unit, without causing a production failure. Smaller corrections in the positions of the printing cylinders and the counter-pressure cylinder relative to each other can be made with the adjustment devices. If the printing cylinders are driven with a non-uniform speed, such that the circumferential speeds change periodically, it is possible to make a quick change in the lengths of the printed-on sections on the material web, for example if the cigarette lengths are to be changed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention is explained in the following with the aid of an exemplary embodiment and with reference to the drawings, to which we refer for all details not mentioned in the specification.

[0018]FIG. 1A is a perspective view of a cigarette rope machine in accordance with the present invention.

[0019]FIG. 2A is a perspective view of a printing unit of the cigarette rope machine of FIG. 1 with a control unit is indicated on an enlarged scale.

[0020]FIG. 3A is a front elevational view of the printing unit shown in FIG. 2.

[0021]FIGS. 4 and 5 are schematic views of characteristic control curves for the printing cylinder driven at non-uniform speeds.

DETAILED DESCRIPTION OF THE INVENTION

[0022] A cigarette-rope producing machine of the cigarette industry, which is produced by the assignee of the present invention and sold under the name PROTOS is shown in FIG. 1. A lock 1 supplies portions of tobacco fibers to a pre-distributor 2. In a controlled operation, a removal cylinder 3 of the pre-distributor 2 fills a storage container 4 with tobacco. A vertical conveyor 5 then removes tobacco from the storage container 4 and supplies it to an accumulation chute 6 in a controlled operation. A pin cylinder 7 removes a uniform stream of tobacco from the accumulation chute 6, which is beaten out of the pin cylinder 7 by a beater cylinder 8 and is thrown onto a distributing web 9 that circulates with a constant speed. A fibrous tobacco web that has formed on the distributing web 9 is thrown into a sifting device 11, which essentially comprises an air curtain through which larger and/or heavier tobacco particles pass while all other tobacco particles are guided by the air into a funnel 14 formed by a pin cylinder 12 and a wall 13. In a tobacco channel 16, the pin cylinder 12 throws tobacco fibers against a rope conveyor 17 where the tobacco is held with the aid of air sucked into a vacuum chamber 18 and is turned into a tobacco fiber rope. A stripper 19 removes excess tobacco from the tobacco fiber rope, which is then placed onto a cigarette paper strip 21 that moves along at the same speed. The cigarette paper strip 21 is pulled from a bobbin 22, is guided through a printing unit 23 and is placed onto a driven format belt 24. The format belt 24 then transports the tobacco rope and the cigarette paper strip 21 through a format machine 26 where the cigarette paper strip 21 is folded around the tobacco rope, with one edge still projecting, to which glue is then applied with a glue applicator (not shown). Following this, the glue seam is closed and dried with a tandem seam smoothing iron 27. The cigarette rope 28 formed passes through a rope-density measuring device 29, which controls the stripper 19, and is then cut into double-length cigarettes 32 by a knife apparatus 31. The double-length cigarettes 32 are then transferred with a transfer unit 34, provided with controlled arms 33, to a takeover cylinder 36 of a filter-attachment machine 37 where they are cut into individual cigarettes on the cutting cylinder 38 by using a circular knife.

[0023] The conveying belts 39, 41 convey excess tobacco to a container 42 arranged below the storage container 4 from which the returned tobacco is removed again by the vertical conveyor 5.

[0024]FIGS. 2 and 3 show a printing unit 23 with two rotating printing cylinders 45, 46 and a counter-pressure cylinder 47. Both printing cylinders 45, 46 make contact with the counter-pressure cylinder 47. A material web in the form of a cigarette paper strip 21 is guided continuously between these cylinders 45, 46, 47. A supply unit (not shown) feeds the printing material, e.g. a printing liquid such as a liquid color, to the printing cylinders at, for example the elevated areas 98 or depressions, which then transfer this material in the form of a mark onto the cigarette paper strip 21. The print marks can be print images of cigarette marks, company logos or other types of designations. The printing cylinders 45 and/or 46, which are driven synchronous with the cigarette paper strip 21 with the aid of the machine drive or separate electric motors 48, 49, are positioned in a bearing support 51 that is formed by two bearing or mounting plates 52, 53 which are spaced apart with a spacing bolt 54. The electric motors 48, 49 are actuated with a control unit 201 that cooperates with a memory 202 and a central machine control unit 200, in the manner described below.

[0025] In FIG. 3, the front mounting plate 52 is omitted for clarity in explaining other aspects of the printing unit 23. The shafts 56 for the printing cylinders 45, 46 and the electric motors 48 and/or 49 are connected via position-defined, form-locking couplings 58, 59, such that the printing cylinders 45, 46 can be axially removed from the shafts of the electric motors 48 and/or 49 that are mounted on the machine. Once printing cylinders 45, 46 are fitted onto the machine, they again assume their predetermined positions relative to the cigarette rope machine. Suitable couplings of the aforementioned type can be Type BK5/BK6 from German corporation R+W Antriebselemente GmbH.

[0026] The printing cylinder 46 and the electric motor 49 are omitted in FIG. 2 for clarity. The printing cylinders 45, 46 can be displaced to some degree in an axial direction with adjustment screws 61, 62 and counter to the effect of springs 64.

[0027] The counter-pressure cylinder 47 is positioned to freely rotate on an spindle 79, such that the counter-pressure cylinder 47 can be moved along by the material strip 21.

[0028] The spindle 79 is positioned inside rubber-elastic bushings (not shown) in the mounting plates 52, 53. The ends of the spindle 79 are held with the aid of ball boxes 77 inside recesses 76, which can be displaced slightly with adjustable screw bolts 71, 72 relative to the mounting plates 52, 53. As a result of deformation of the rubber-elastic bushings, the counter-pressure cylinder 47 can be adjusted relative to the printing cylinders 45, 46.

[0029] The fastening device 86 for attaching and detaching the bearing support 51 to and/or from a machine wall 87 is provided with a bolt 88 that extends through bores 89 in the mounting plates 52, 53 and supports the bearing support 51. An end region 88 a of bolt 88 can be screwed together with the machine wall 87. A lever 92, which is used to attach and detach the bolt, is positioned on the other end 88 b of the bolt 88.

[0030] If a printing unit 23 is to be replaced, the bolt 88 is detached from the machine wall 87 by turning the lever 92 and the printing unit, which can be held with a handle 66, and the printing unit is pulled off in an axial direction. In the process, the shafts for the printing cylinders 45, 46 are separated at the coupling locations from the shafts of the electric motors 48 and/or 49. The new printing unit 23, for which the printing cylinders 45, 46 are advantageously pre-mounted and pre-adjusted, is then fitted on by reversing these steps, wherein the shafts of the printing cylinders are form-fittingly connected to the shafts of the electric motors at the coupling locations.

[0031] The continuously moving material strip 21 is imprinted by one or several synchronously driven printing cylinders. This means that the printing unit must be replaced for format changes that require a change in the length of the cigarettes. According to a further exemplary embodiment of the invention, the lengths of the printed-on sections can be adapted by changing the rotational speed of the printing cylinders between two printing operations, in which the speed must be synchronized. If the printing cylinders are operated at a faster speed between two synchronous runs, the lengths of the sections are shortened and vice versa. One exemplary embodiment of realizing the method of the present invention is shown below with the aid of an example describing the control unit for the motor 48.

[0032] The central machine control unit 200 supplies a synchronous first clocking signal to the control unit 201 for the continued movement of the material web 21. This signal can, for example, have one clocking pulse per millimeter rope movement and exhibits only slow frequency changes because it is coupled to the inertia of the main drive systems for the machine. The control unit, in turn, supplies a second clocking signal to the motor 48, embodied as stepping motor, which realizes a rotational step with each clocking pulse of the second signal. In the process, the motor can perform a full rotation, for example, for every 1000 clocking pulses. The control unit 201 is provided with a frequency multiplier 204 and emits a third clocking signal, e.g. one that has one thousand times the frequency of and is synchronous to the first clocking signal. This third clocking signal is fed to a counter 203 which respectively emits a clocking pulse of the second clocking signal, provided it has registered a predetermined number of clocking pulses of the third clocking signal that are referred to as dividers.

[0033] As a simple example, the printing cylinder 45 has a circumference of 130 mm and the printing unit 23 is used to apply printed images, spaced apart 130 mm, to the material web 21. While transporting the material web over a distance of 130 mm, the central machine control unit 200 transmits 130 clocking pulses of the first clocking signal to the control unit 201. The frequency multiplier 204 turns these into 130,000 clocking pulses of the third clocking signal. The divider specified for the counter 203 is 130, so that for the 130,000 clocking pulses of the third clocking signal, it transmits 1000 clocking pulses of the second clocking signal to the motor 48 and this motor consequently performs a full rotation. In the process, the printing cylinder 45 and the material strip 21 always move at the same speed.

[0034] According to a different example, the printing unit 23 is used to apply printed images with a spacing of less than 130 mm to the material strip 21. A digital characteristic line 300 is stored for this in the memory 202, such as the one shown in FIG. 4. The position of the memory locations is plotted on the axis 301 and the value for the divider that is stored in the memory location is plotted on the axis 302. For each clocking pulse of the first clocking signal, the following divider value is read out of the memory and is transmitted to the counter 203. In the process and while the elevated area 98 on the printing cylinder 45 makes contact with the material web, the value for the divider corresponds to the value 303 during the synchronous operation, i.e., 130 for example. Once the elevated area 98 lifts off the material web 21, lower divider values are transmitted to the counter 203 such that the frequency of the second clocking signal and thus the rotational speed of the motor 48 and the printing cylinder 45 increases. As a result, the value of the divider is reduced in the form of a flat ramp such that the motor load is only a low acceleration moment. Following approximately half a motor 48 rotation, the divider values are again raised slowly until the divider once more reaches the value 303 during the synchronous operation before there is renewed contact between the elevated area 98 and the material web.

[0035] Following the completion of one rotation (line 304), the motor 48 sends a signal to the memory 202, whereupon the divider values are again read out of the first memory area.

[0036] In order to apply print marks with a spacing of more than 130 mm to the material strip 21, the characteristic line 310 stored in the memory 202 for the divider value has higher divider values if there is no contact between the elevated area 98 and the material web 21 than for the synchronous operation. A characteristic line of this type is shown in FIG. 5. The elements shown in FIG. 5 correspond to those in FIG. 4 and are provided with reference numbers that are raised by 10. In other words, axis 311 is the position of the memotry location and axis 312 is the value for the divider stored in the memory location. Value 313 is the value at which the printing cylinder makes contact with the web, and value 314 is the value at the completion of one rotation.

[0037] In a printing unit with several printing cylinders, a control unit 201 with a memory 202 can be provided for each printing cylinder. The elements 200 to 204 in FIG. 2 are functional elements which can be realized in the software of an automatic control unit or a control computer.

[0038] The invention has been described in detail with respect to preferred embodiments, and it is will now be apparent from the foregoing to those skilled in the art, that changes and modifications may be made without departed from the invention, therefore, as defined in the appended claims, is intended to cover all such changes and modifications that fall within the true spirit of the invention. 

1-23. (canceled).
 24. A printing unit for applying print marks to a wrapping strip in a cigarette rope machine of the tobacco processing industry, said unit comprising: at least one printing cylinder; a counter-pressure cylinder in contact with the at least one printing cylinder; and a fastening device adapted to jointly attach and detach the at least one printing cylinder and the counter-pressure cylinder to the cigarette rope machine.
 25. The printing unit according to claim 24, further comprising a bearing support, wherein the at least one printing cylinder and the counter-pressure cylinder are mounted on the bearing support such that the fastening unit attaches and detaches the unit to and from the machine as a single unit.
 26. The printing unit according to claim 25, wherein the bearing support includes two bearing plates between which the at least one printing cylinder is arranged.
 27. The printing unit according to claim 24, further comprising a spindle, wherein the counter-pressure cylinder is positioned so as to rotate freely on the spindle, and wherein the at least one printing cylinder is adapted to be driven by at least one electric motor.
 28. The printing unit according to claim 25, wherein the fastening device is connected to the bearing support.
 29. The printing unit according to claim 28, wherein the fastening device includes a bolt that supports the bearing support, and wherein the bolt has one end to be screwed into a machine wall of the machine.
 30. The printing unit according to claim 29, further comprising a lever at the other end of the bolt for detaching or fastening the bearing support.
 31. The printing unit according to claim 29, wherein the bearing plates have bores through which the bolt extends.
 32. The printing unit according to claim 27, further comprising a position-specified coupling provided between the at least one electric motor and the at least one printing cylinder such that, upon installation of the printing unit, the at least one printing cylinder assumes a predetermined angle of rotation position within the cigarette rope machine.
 33. The printing unit according to claim 24, further comprising an adjustment device for positioning the counter-pressure cylinder relative to the at least one printing cylinder.
 34. The printing unit according to claim 33, wherein the adjustment device includes at least one screw bolt.
 35. The printing unit according to claim 33, further comprising an elastic, resilient bearing element for the spindle of counter-pressure cylinder to allow for an adjustment movement.
 36. The printing unit according to claim 24, wherein the at least one printing cylinder includes at least two printing cylinders.
 37. The printing unit according to claim 27, further comprising a control unit for transmitting control pulses to the drive motor such that the rotational speed of the printing cylinder at a time at least one of before and after a printing operation deviates from the rotational speed during the printing operation.
 38. The printing unit according to claim 37, wherein the wrapping strip is a continuously moving material web passing between the at least one printing cylinder and the counter-pressure cylinder, and wherein the counter-pressure cylinder moves at the same speed as the at least one printing cylinder during the printing operation, but moves at a deviating speed at a time at least one of before and after the printing operation.
 39. The printing unit according to claim 37, wherein the at least one printing cylinder includes at least two printing cylinders in contact with the counter-pressure cylinder.
 40. The printing unit according to claim 37, wherein the motor driving the at least one printing cylinder is a stepping motor, wherein the control unit transmits control pulses to the stepping motor at a predetermined constant frequency for a synchronous movement of the at least one printing roller and the material web during the printing operation and at a second frequency for a deviating movement between two printing operations.
 41. The printing unit according to claim 40, wherein the control unit includes a memory for storing the predetermined frequencies of the control pulses.
 42. A method for periodically applying print marks to a wrapping strip of the tobacco industry, comprising the following steps: supplying the wrapping strip at a first speed to an operating range of a printing cylinder; rotating the printing cylinder at a second speed; and applying a print mark to the wrapping strip with the printing cylinder; wherein the first and second speeds are approximately equal while the print mark is being applied to the wrapping strip, and wherein the first and second speeds deviate from one another at least part of the time while no print mark is being applied to the wrapping strip.
 43. The method according to claim 42, further comprising changing second speed periodically.
 44. The method according to claim 43, wherein the changing step includes activating a stepping motor with control pulses having an alternating frequency.
 45. The method according to claim 44, wherein the activating step includes determining the frequency according to a stored characteristic curve.
 46. The method according to claim 45, wherein the activating step includes additionally determining the frequency in accordance with the first speed. 